Field of the Invention
The present invention relates to a three-dimensional net-like structure used for mattresses and cushions, as well as to a manufacturing method of three-dimensional net-like structure and a manufacturing apparatus of three-dimensional net-like structure.
Description of the Related Art
The conventional method of forming four faces of a three-dimensional net-like structure described in PTL1 extrudes downward filaments of a thermoplastic synthetic resin as the material or the primary material in a molten state from a die with a nozzle end including a plurality of holes and thereby makes the filaments freely fall between partially submerged haul-off machines. The filaments are hauled off at a lower haul-off speed than the fall speed to form the three-dimensional net-like structure. This method uses two pairs of opposed haul-off machines to form a rectangular shape in a direction perpendicular to the extruding direction. The distance between the pair of opposed haul-off machines is set less than the width of the extruded filament assembly. All the four peripheral surfaces of the filament assembly come into contact with the haul-off machines to be formed in shape before or after the filament assembly is submerged. All the four peripheral surfaces of the resulting three-dimensional net-like structure parallel to the extruding direction accordingly have the higher density relative to the density of the remaining part other than the surfaces. This method enhances the alignment of the filaments without requiring any post finishing.